The contest is pretty simple. To participate, the doughnut and coffee chain is asking people to "share how they are celebrating St. Patrick's Day with Dunkin' Donuts" with the hashtags #DDLuckyDozen and #Sweepstakes for the chance to win. Follow the chain on Twitter, post a picture of yourself in pre-celebration mode for St. Patrick's Day and include the hashtags. The contest is also open on Instagram.

One very, very lucky fan will win a trip to Dunkin's headquarters in Boston, where they'll be able to create their own signature doughnut (the possibilities are endless!) with the brand's chefs in the chain's official test kitchen.

It's a trip the chain estimates is worth $1,500. The contest is now open but it closes on St. Patrick's Day.

The 12 doughnut fans who come in second place will win a gift card worth $286, which the chain says works out to about five doughnuts per week for a year.

Dunkin's new mint brownie creation, part of its first-ever partnership with the Girl Scouts of the USA, is basically a Thin Mint cookie transformed into a doughnut and features a yeast doughnut filled with mint chocolate brownie batter-flavored buttercreme, that's topped with green dipping icing and sprinkled with brownie crumbles. The chain also has limited-edition beverages with three coffee flavorings: Thin Mints, Coconut Caramel (a riff on Samoas) and a classic peanut butter cookie.

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